Not surprising. In my experience, sitting isn't necessary. Pain is overcome through not having a preference of having comfort and avoiding discomfort. For instance, it's winter. On a cold winter day, some people shiver, whine, and think about how cold it is. A Zen meditator thinks, "This body is cold, but this body is notself," therefore there is no discomfort. Not just in cold weather, though. But when they enter a warm area, like entering a warm environment after leaving a cold one, like a hot shower on a cold day, they don't think, "Ahhh! Relief!" because it is only the body that gets cold and warm, not the self; one's Buddha nature is not expressed due to temperature changes.

These kinds of news are good only for advertising Zen a bit but nothing else. 13 unknown people compared to 13 other unknown people and it happens that some of one group manage pain better than others. Very informative. We don't even know which Zen they were practising and how.

"There is no such thing as the real mind. Ridding yourself of delusion: that's the real mind."(Sheng-yen: Getting the Buddha Mind, p 73)